Organic solar cells are being developed for clean renewable energy due to their potential for making cost-effective, large area devices. The performance of solar cells depends on the light-absorbing semiconducting materials. Alternating conjugated polymers based on backbone structures of benzo[1,2-b:3,4-b′]dithiophene (BDT) and benzo[1,2-b:3,4-b′]dithiophene-thienothiophene (BDT-TT) have demonstrated promising performance in organic solar cell applications. The symmetric, planer structure of BDT provides excellent charge carrier mobility and optical absorption properties to the polymer. However, the BDT conjugated polymer based solar cells are relatively inefficient due to inadequate optical absorption, relatively low charge carrier mobility and non-optimized device morphology.
Anthradithiophene (ADT) has an expanded conjugation system compared to BDT, and ADT-based conjugated polymers would have a further expanded conjugation system compared to BDT-TT. Further, ADT has a suitable highest occupied molecular orbital (HOMO) energy and solid state structure for use as a p-channel thin film transistor (TFT) semiconductor with high mobility. Thus, ADT-based conjugated polymers are needed with a further expanded conjugation system to cover an even broader solar spectrum and with a tuned polymer packing to optimize the device morphology and enhance charge carrier mobility.